FIG. 1 depicts a block diagram of a multimedia system according to the H.324 standard. In the block designated by reference numeral 1 are accommodated the modules which are defined in greater detail in H.324. Video codec 2 is configured in accordance with the method in ITU-H.263/H.261. In order to smooth out any time differences between the image coding and the sound coding, a delay device 4 is connected downstream of audio codec 3 in accordance with ITU G.723. Device 5 functions to process data protocols, e.g., V.14 LAPM, etc., and device 6 processes control protocols in accordance with ITU H.245. The audiovisual data is supplied to codecs 2 and 3 by appropriate I/O (Input/Output) devices 7 and 8. The devices for processing protocols 5 and 6 receive their input data via devices 9 (User Data Applications) and 10 (System Control). The data streams of codecs 2, 3 and of protocol processing devices 5 and 6 are joined via multiplex/demultiplex device 11 in accordance with the H.223 standard. Modem 12, connected downstream, supplies V.34 conformal data for the combined data streams and V.25 conformal data for the system control data. Transmission network 13 is connected to block 1, along with an appropriate network control system 14.